Gun sight



Patented Apr. 1 7, 1951 UNITED STATES PATENT ff@ KQ@ OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 4 Claims.

This invention relates to sighting apparatus for guns and more particularly to sighting apparatus for use with guns mounted on a moving lehiclasuchasashipprairplane.

When a gun is fired from a moving vehicle, the movement of the gun platform affects the velocity and the direction of travel of a projectile fired from the gun. In order to compensate for the effect of the gun platform motion on the flight of the projectile, it is necessary to put into the gunsight a correction for mhintslnotion. This is a function of the speed of the platform and of angles of elevation and train of the Ygun with respect to the direction of" travelv of the gun platform.

In firing against a stationary target, correction for own ships motion is the main correction, while in firing against a moving target, a correction for target motion must also be introduced into the gunsight.

An object of this invention is the provision of electrical means for automatically positioning the sighting element of a gunsight. By using electrical means, complicated mechanical linkages are avoided and the addition of other corrections, such as for target motion, is simplified.

Another object of the invention is to provide electrical means for positioning a sighting element to compensate for own ships motion which operates automatically with a relatively small amount of human assistance.

Another object of the invention is to provide a device of the character referred to above which is simple and accurate in operation and which is of relatively small size and Weight.

Another object of the invention is to provide a mechanism for correcting a sighting element to compensate for own speed which can be readily installed on existing equipment by simple modifications involving connections to elevation and train mechanisms at convenient places and the transmission of correction data by wiring.

These and other objects of the invention will be apparent from the following specication and the accompanying drawing, in which Fig. l is a composite view partly in perspective and partly in schematic form, illustrating the new sight correcting device; and

- Fig. 2 is a wiring diagram of the motor operating circuits represented by the numerals 3'I and 55 in Fig. 1.

In the drawing, the numeral I represents a sighting element such as a gunsight telescope, the reticule or reflecting element of a collimating reector type gunsight, or other type of sighting element. By shifting the position of the element I0 horizontally and vertically, sighting corrections are introduced into the gunsight. As shown, the sighting element I0 is pivotally mounted on a support II so that the sighting element may be elevated and depressed by tilting as the sighting corrections are introduced. The sighting element is elevated and depressed by means of a rearwardly extending arm I2 connected by linkage I 3 with arm I4 of a geaIl segment I5 which is pivotally mounted on support II for rotation in a vertical plane. A reversible electrical motor I6, which will be called the elevation motor, rotates a worm Il meshing with the gear I5 to elevate or depress the sighting element on rotation of the motor, depending upon the direction of rotation of the motor. Motor I6 also rotates a worm or screw I8 upon which is mounted a movable potentiometer contact I9 having internal helical grooves which coact with worm I8, causing the contact I9 to move along the worm I8 when motor I6 is operated. Contact I 9 coacts with a potentiometer 20 which serves a purpose to be described presently.

Motor I6, support II, and potentiometer 20 are mounted on a supporting platform 2| which is pivoted on a stationary support 22 so as to be rotatable in a horizontal plane. Platform 2| carries an integral gear segment 23 disposed in a horizontal plane and meshing with a worm gear 24 which is rotated by a reversible electrical motor 25 through a helically grooved rotatable shaft 26. A movable potentiometer contact 2l is mounted on the shaft 26 and, because of the helical groove in the shaft, is moved back and forth along shaft 26 by rotation of the motor. The contact 2l co-acts with Ia potentiometer 28 for a purpose which will be described presently. The motor 25 operates through the gears 25 and 23 to position the sighting element I IJ in train.

The means by which the sighting element positioning motors I6 and 25 `are actuated to put train and elevation corrections into the sighting.

element l0 will now be described. Own ships speed corrections can be expressed as a function of the velocity of the gun platform, as a function varying approximately as the sine of the train angle for train correction, and as the sine of the elevation angle multiplied by the cosine of the train angle for the elevation correction. By using potentiometers, an electrical solution is obtained for any desired corrections, and any com-f bination of corrections is easily made electrically and the resultant value put into the sight elements.

In the drawing, a battery or other source of electrical energy 29 is utilized to supply power for the sight. A pair of potentiometers 38 and 3| is connected in parallel across the battery. Movable contacts 32 and 33 are mounted for movement along potentiometers 30 and 3|, respectively, the movable contacts being mounted on a common shaft 34 which is rotatable by a speed setting knob 35 by which the velocity oi the vehicle is set into the sight correcting circuit. This setting may conveniently be done automatically by means obvious to one skilled in the art.

The movable contact 32 of potentiometer 38 is connected to one end of the winding of a potentiometer 36, the other end of the winding being connected to the negative side of the current source 29. A fixed center tap 36a on, potentiometer 36 is connected to a center tap 28a on potentiometer 28. A movable contact 38 on potentiometer 36 is connected to contact A of the motor operating circuit shown in Fig. 2 and denoted generally by the numeral 31. Circuit 31 is represented in Fig. 1 by a box bearing the numeral 31 in the train adjusting circuit, and it should be noted that a similar circuit is utilized in the elevation correction circuit where it is denoted by the numeral 55.

Contact 38 is connected through a Scotch yoke 39 to Wheel 4|) which is rotated by a shaft 4| driven by gear 42. The gear wheel 42 meshes with a stationary gear (not shown) on the gun mount so as to be rotated as the gun moves in train. By this arrangement, the potential taken off the potentiometer 36 -by the movable Contact 38 varies as the sine of the train angle of the gun.

The movable contact 21 on potentiometer 28 is connected to contact B in circuit 31 so that when potentiometers 36 and 28 are not balanced, a potential exists across contacts A and B which variesA in sign and magnitude depending upon the state of unbalance of the two potentiometers. The motor operating circuit 31 which is duplicated at 55 includes a pair of solenoids 31a and 31b having their windings connected by wires 43 and 44 in parallel relation across terminals A and B. The circuits for coils 31a and 31h also include rectiers 45 and 46, respectively, which permit a flow of positive current to solenoid 31a only from terminal A, and to solenoid 31h only from terminal B. This assures that only solenoid ,31a operates when A is positive and B is negative, and assures that only solenoid 31h operates when B is positive and A is negative. Solenoids 31a and 31h operate a normally neutral reversing switch 45a which controls the flow of current from the current source 29 through terminals C and D to the brushes of motor` 25 which are connected to terminals E and F of circuit 31. The field coil 25a of motor 25 is shown connected directly to the source of current 29 for the sake of simplicity but a switch may conveniently be added to switch 45a so that the motor eld coil is energized only when either solenoid 31a or 31b is energized.

It is obvious that the position of the movable contact 38 on potentiometer 36 is a function of the position of the gun in train. It is also obvious that for every position of the movable contact 38, there is a corresponding balancing position of the sliding contact 21 in which there is no potential across terminals A and B. When contact 38 is moved by movement of the gun in train to a position which unbalances the relation between contacts 38 and 21, a potential is set up across terminals A and B, the sign and magnitude of which depends on the state of unbalance of the two potentiometers. When the potential is positive at A and negative at B, solenoid 31a is operated, solenoid 31h being prevented from operating by rectifier 46. Operation of solenoid 31a moves reversing switch 45a from its neutral position to a position wherein current is transmitted from the current source 29 to the brushes of motor '25 to operate the motor. The operation of the motor rotates shaft 26 which moves the Sighting element and at the same time moves slider 21 along potentiometer 28. As soon as contact 21 reaches a position of balance with contact 38, the potential across terminals A and B no longer exists, solenoid 31a is consequently no longer energized, and reversing switch 45a returns to its neutral position, whereupon the brushes of the motor are no longer energized and the operation of the motor ceases. When this state of balance is achieved, the sighting element is correctly positioned in train to compensate for the effect of own ships motion on the flight of the projectiles. If the opposite potential is impressed across terminals A and B, solenoid 31h is energized and the switch 45a is actuated in the opposite direction to that described above, causing the brushes of the motor to be energized in the opposite direction to that just described, and resulting in operation of the motor and shaft 26 in the corresponding direction to move the sighting element and contact 21 until the two potentiometers are balanced, whereupon the operation of the motor ceases.

To correct the position of the sighting element in elevation, circuits similar to those described above are utilized except that an additional potentiometer is utilized in order to vary the position of the sighting element in elevation as a function of the sine of the elevation angle multiplied by the cosine of the train angle. To make this correction, sliding contact 33 of the velocity potentiometer 3| is connected to one end of the winding of a potentiometer 41 which has a movable contact 48 whose position on potentiometer 41 is controlled through a Scotch yoke connection 49 by movement of the gun in train. The other end of the potentiometer winding is connected to the negative side of current source 29. A iixed center tap 5| on potentiometer 41 is connected to one end of the winding of a potentiometer 50, the other end of the potentiometer winding being connected to the movable contact 48 on potentiometer 41. A fixed center tap 53a on potentiometer 50 is connected to xed center tap 54a on potentiometer 28 while a movable slider 52 on potentiometer 58 is connected to terminal A of motor controlling circuit 55 which is a duplicate of circuit 31 described above. Movable contact 52 is moved by a Scotch yoke connection 53 actu ated by a gear wheel 54 which is rotated by its engagement with a xed gear as the gun moves in elevation. Scotch yoke 49 is arranged so that the output from movable contact 48 varies as the cosine of the train angle of the gun and the Scotch yoke connection 53 is arranged so that the output from the movable contact 52 varies as the sine of the elevation angle of the gun. By combining the two potentiometers as described, the final output from the movable contact 52 represents the original potential from movable contact 33 varied as the cosine of the train angle multiplied by the sine of the eleva- `the speed indicator o tion angle of the gun. The movable contact |9 of potentiometer 20 is connected to terminal B of circuit 55 and motor I6 is controlled by switch 45a of circuit 55, the state of unbalance of the positions of potentiometers 50 and 20 controlling the operation of motor I which positions the sighting element in elevation, the sighting element being correctly positioned in elevation when the potential across terminals A and B of circuit 55 is zero.

By the use of the device as explained above, a sighting correction for train is set into sighting element l0, which sighting correction is a function of the gun platform velocity and of the train angle of the gun. An elevation correction is also set into sighting element l0, which correction varies approximately as the velocity of the gun platform and as the sine of the elevation angle multiplied by the cosine of the train angle of the gun. These corrections are achieved by means of potentiometers and without the use of complicated mechanical linkages which would induce error, increase the Weight, size, and possible sources of error of the device.

The cards upon which potentiometers 36, 41 and 50 are wound may be of any desired shape so as to compensate or correct for other factors which enter into the sight correction problem. The sine and cosine values mentioned above are close approximations of the exact functions and by varying the shapes of these cards, these values may be made more exact.

If translational lateral or vertical movement of the sighting element is desired when the invention is used with other types of sights, suitable rack and pinion or other gearing may be operated by the motors I6 and 25 to position a sighting element. I also desire to include Within the scope of the invention the positioning of the sighting element by other electrical means besides motors.

If it is desired to correct for only "own ships motion, no human sight setting need be done, provided the speed indicator 35 is connected-to e vehicle upon which the gurfs'ounted so as to be automatically varied as the velocity of the vehicle varies. This may be easily done by shafting, servomotors, or other` well known means.

If desired, the electrical herein may be used with a cathode ray tube gunsight as described in my abandoned application Serial No. 510,403, iiled November 15, 1943, or with other sight indicating means. In use with the cathode ray tube sight, the potential across terminals A and B of circuits 31 and 55 caused by unbalance of the potentiometers would be used to deflect the image on a cathode ray tube which provides a sighting image in a reflector type sight.

While this device is particularly adapted for putting "own ships motion corrections into a gunsight, it can be electrically connected to a device for determining corrections for target motion so that the two sets of corrections can be combined electrically into one sight, thus taking care of all of the major factors in the sightv setting problem.

In the claims, the sighting element is spoken of as being incorrectly positioned when it is so positioned that the sighting corrections which the invention is intended to make in the position of the sighting element have not in fact been made.

The invention herein described may be manusystem described 8- factured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

l. In a gunsight having a sighting element for use with a gun mounted on a moving platform, a device for correcting the position of said sighting element to compensate for own ships motion, comprising means for producing a rst electrical potential proportional to own speed, a first circuit for varying said potential approximately as the sine of the train angle of the gun with respect to the direction of motion of the platform, means operable by the resultant potential from the first circuit for positioning said sighting element in train, a second circuit for varying said iirst potential as the cosine of the train angle of the gun with respect to the direction of motion of the gun platform and for varying the resultant potential as the sine of the angle of elevation of the gun, and means operable by the final resultant voltage from said second circuit for positioning the sighting element in elevation. y

2. In a gunsight having a sighting element for use with a gun mounted on a moving platform; a lrst reversible electric motor for positioning said sighting element in train; a second reversible electric motor for positioning said sighting element in elevation; a control circuit for said iirst motor comprising a current source, a first potentiometer having a movable contact whose position is a function of the velocity of the platform, a second potentiometer having a xed center tap and having its Winding connected to said movable contact and to said current source, a movable contact on said second potentiometer Whose position varies as the sine of the train angle of the gun with respect to the direction of motion of said platform, a third potentiometer having its Winding energized by said current source and having a fixed center tap connected to the fixed center tap of said second potentiometer and a contact movable by rotation of said first electric motor, and a normally open reversing switch connected between said current source and said first motor, said switch being operable in response to the potential across the movable contacts of said second and third potentiometers to actuate said motor for simultaneously positioning said sighting element in train and moving said third movable potentiometer contact until the potential across said second and third movable contacts is balanced out, whereupon said switch opens and operation of said motor ceases; a control circuit for said second motor comprising a current source, a fourth potentiometer having a movable contact whose position is a function of the velocity of the platform, a fifth potentiometer having a fixed center tap and having its Winding connected to said fourth movable contact and to said current source, a movable contact on said fifth potentiometer whose position varies as the cosine of the train angle of the gun with respect to the direction of motion of said platform, a sixth potentiometer having a fixed center tap and having its Winding connected to said fifth movable contact and to said fifth center tap, a movable contact on said sixth potentiometer whose position varies as the sine of the elevation angle of the gun, a seventh potentiometer having its Winding energized by said current source and having a xed center tap connected to the fixed center tap of said sixth potentiomelibti Hunan 7 ter, a contact on said seventh potentiometer movable by rotation of said second motor, and a second normally open reversing switch connected between said current source and said second motor, said second switch being operable in response to the potential across the movable contacts of said sixth and seventh potentiometers to actuate said motor for simultaneously positioning said sighting element in elevation and moving said seventh movable potentiometer contact until the potential across said sixth and seventh movable contacts is balanced out, whereupon said switch opens and operation of said motor ceases. 3. In a gun sight having a sighting element for use with a gnn1nounted,on-a lnoving.platform, a reversible electric motor operatively connected to said sighting element to adjust the position of said element, a relay actuated by potential differences to operate said motor, mean,Sflllusp1-lp-ply ing a rst potential to said relay xviii h is a functionof` thevelocityof.saidplatfornndo the sine of the train angle of said gun, and follow-up means to supply a second potential to said relay different from said rst potential When the velocity of said platform or the position of the gun in train is changed.

4. In a gun sight having a sighting element for use with a gun mounted on a moving platform, a reversible electric motor operatively connected to 8 said sighting element to adjust the position of said element, al relay actuated by potential differences to operate said motor, means for supplying a first potential to said relay which is a function of the velocity of said platform and of the product of the cosine of the angle of train and the sine of the angle of elevation of the gun, and follow-up means to supply a second potential to said relay different from said rst potential when the velocity of said platform or the position of the gun in train is changed.

PHILLIP ROOD WHEELER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,343,003 Morse June 8, 1920 1,650,628 Inglis Nov. 29, 1927 2,399,726 Doyle et al May 7, 1946 2,408,681 Pontius et al Oct. l, 1946 2,426,658 Woolridge Sept. 2, 1947 2,429,467 Ketay 2 Oct. 21, 1947 2,433,843 Hammond et al 1 Jan. 1, 1948 2,463,182 Ketay Mar. 1, 1949 2,471,278 Meachum May 24, 1949 2,504,168 Wheeler Apr. 18, 1950 

